throat

[bigted]

I know this has been addressed before but been cogitating on it for awhile so thought id gather some thoughts here.

most of my rifles have a fairly abrupt beginning for the rifling. so I reason that if this lead section rite at the beginning of the rifling was less abrupt ... then the success of paper patching with smokeless powder would increase by a bunch.

in other words ... if the rifling would have say instead of what looks like a fairly steep angle on the beginning of the rifling such as a 45 degree angle ... spread it out to a nice even angle at the beginning of the rifling to say somewhere in the 10 degree angle and a bit longer in the transition should be more gentle on the patch and improve the accuracy because the patch should get ironed on instead of taking a chance on partial stripping or even a full strip ... followed by the lead mining needed to return the rifle to accurate shooting.

so if a feller would smooth the rifling beginning ... what would the effect be on a jacketed or even our grease groove cast bare boolits?

this has been discussed before but id like to begin another posting on the subject to raise the question once again.

[johnson1942]

both my .45/70/s have .459 throats. i bought a clymer .459 throating reamer when i bought the guns and did it my self. they are about a inch long. they shoot cast bullets very very well. however i only shoot paperpatch in them now i can set the bullet out of the case further and up in to the throat which is into the barrel. they are tackdrivers. i remember reading of a sharps that had a smooth bore 1/2 way down the barrel. thats a long throat. it probably wasnt a original barrel but when shot it shot very very well. 16 inches of smooth bore and 16 inches of rifling. didnt harry pope throat some of his? i got the idea from some where, and really like it.

[barrabruce]

+1
Differnce would be the same as as a sizing die..sharp shoulder versus tapered leade angle.

I think that modern throats are just a cheap 'n easy maufacturing cop out.
Cheaper being longer tool life and easier chambering.
A sharp shoulder..think counter sink drill is easy to obtain finnish than a longer angle which needs more cleaning and a delicate touch to get a good finish.

Just me 2 cents worth.

[bigted]

rite on ... I cant think of any area where the nice smooth taper into the rifling would be harmful. this gentle ... ramp if you will ... isn't a throat proper that I refer to ... it is just the more gentle lead into the full rifling instead of the abrupt transfer from what throat you have and full rifling.

i tend to agree with barrabruce in that it is most probably a production thing ... rather then any accuracy advantage that gives us this rather abrupt transition into the full depth rifling. even with jacketed bullets I can see no advantage in going from slick throat to full rifling in just a 1/64th of an inch.

[Nobade]

OK, chamber throats are something I deal with on a continuous basis thanks to my work. The deal with them is there are a wide variety, and they mostly exist as they do according to the thinking which was current when they were produced. If you look at older designs like most of the WCF rounds, they have little if any step at the mouth of the chamber and a fairly gentle leade angle. They were designed for use with black powder and lead bullets. Now look at the 375 H&H and 30-06. They were designed to be used with jacketed bullets and smokeless powder, under demanding field conditions, and made to work. They look different. Now look at something like the 6.5 Creedmoor. Completely different thought pattern. Designed for maximum accuracy, with its parallel section only .001 over bullet diameter, and 1.5 deg/side leade. But no room for dirt or fouling. Each of the SAAMI cartridges has a particular design for a reason, and that design has absolutely nothing to do with cost cutting during manufacturing. It costs nothing extra to make the throat on a reamer any different from any other shape.

Now what we run into when playing with paper patched boolits is some designs work better and are easier to deal with than others. Tapered throats with no or little parallel, like most military rifles have, are the easiest to use since they typically start out a lot bigger than the groove diameter and slowly taper to the bore. That makes them pretty forgiving of boolit diameter, just like they were designed to be. But modern accuracy type throats like that Creedmoor, while they shoot like blazes with jacketed bullets, are difficult to work with using PP Boolits because it needs to be exactly the same diameter as a J bullet or it's not going to go into the hole.

Some designs, like the 45-70, 30 Carbine, 35 Rem, 32-20, and others don't really have a throat. Just a bevel on the back side of the rifling. They work fine if you use them as they were designed but become difficult in the extreme when employed with PP boolits because you can't close the action without bunching up the patch. Some of those can be helped by judicious use of a throating reamer, very minimally, and still be able to work with the loads they were designed for. But getting carried away and putting a huge long throat in them will almost always cause them to not work very well with anything, especially if dealing with a repeater design and wanting ammo to still work through the feeding mechanism. And that is another reason why throats are like they are. Actions have a certain fixed length of ammo that they will feed. A Winchester '73 or '92 or whatever will not work with ammo that is too long. But if the chamber has a longer throat in it, it wants longer ammo for best accuracy. There is a relationship there...

Here is a link to SAAMI. Take a look at the .pdf docs that have chamber and ammo drawings.
http://www.saami.org/specifications_...tion/index.cfm
You will get to see the wide variety of designs out there, and can clearly see some are more appropriate for paper patching than others are. Some are really stupid looking, but if you try to go back to the constraints of the original designer they start to make more sense. They just may not be what YOU want for whatever you are doing, and that is why we have custom reamer makers.

-Nobade

[bigted]

thanks for that Nobade. that makes a lot of sense. however maybe I got miss understood about what exactly I am referring to.

tha sharp 'angle' I speak of and refer to is the abrupt edge on the groove section of the rifling beginning ... not the throat nor lack thereof.

was just over on the BP Patching section and Lead Pot posted photos of a very nice lead section that includes the throat and lead angle that I refer to. the abrupt rifling beginning on the groove section is the area of concern to me and I do not want to add more throat to any current chamber ... just smooth out the "lead angle" on the rifling.

guess my header was misleading a bit ... should have read {RIFLING LEAD ANGLE} srry for the cornfusion.

[barrabruce]

Well I think I'll just stick my head in and shut the f... up from now on.

[mikeym1a]

OK, chamber throats are something I deal with on a continuous basis thanks to my work. The deal with them is there are a wide variety, and they mostly exist as they do according to the thinking which was current when they were produced. If you look at older designs like most of the WCF rounds, they have little if any step at the mouth of the chamber and a fairly gentle leade angle. They were designed for use with black powder and lead bullets. Now look at the 375 H&H and 30-06. They were designed to be used with jacketed bullets and smokeless powder, under demanding field conditions, and made to work. They look different. Now look at something like the 6.5 Creedmoor. Completely different thought pattern. Designed for maximum accuracy, with its parallel section only .001 over bullet diameter, and 1.5 deg/side leade. But no room for dirt or fouling. Each of the SAAMI cartridges has a particular design for a reason, and that design has absolutely nothing to do with cost cutting during manufacturing. It costs nothing extra to make the throat on a reamer any different from any other shape.

Now what we run into when playing with paper patched boolits is some designs work better and are easier to deal with than others. Tapered throats with no or little parallel, like most military rifles have, are the easiest to use since they typically start out a lot bigger than the groove diameter and slowly taper to the bore. That makes them pretty forgiving of boolit diameter, just like they were designed to be. But modern accuracy type throats like that Creedmoor, while they shoot like blazes with jacketed bullets, are difficult to work with using PP Boolits because it needs to be exactly the same diameter as a J bullet or it's not going to go into the hole.

Some designs, like the 45-70, 30 Carbine, 35 Rem, 32-20, and others don't really have a throat. Just a bevel on the back side of the rifling. They work fine if you use them as they were designed but become difficult in the extreme when employed with PP boolits because you can't close the action without bunching up the patch. Some of those can be helped by judicious use of a throating reamer, very minimally, and still be able to work with the loads they were designed for. But getting carried away and putting a huge long throat in them will almost always cause them to not work very well with anything, especially if dealing with a repeater design and wanting ammo to still work through the feeding mechanism. And that is another reason why throats are like they are. Actions have a certain fixed length of ammo that they will feed. A Winchester '73 or '92 or whatever will not work with ammo that is too long. But if the chamber has a longer throat in it, it wants longer ammo for best accuracy. There is a relationship there...

Here is a link to SAAMI. Take a look at the .pdf docs that have chamber and ammo drawings.
http://www.saami.org/specifications_...tion/index.cfm
You will get to see the wide variety of designs out there, and can clearly see some are more appropriate for paper patching than others are. Some are really stupid looking, but if you try to go back to the constraints of the original designer they start to make more sense. They just may not be what YOU want for whatever you are doing, and that is why we have custom reamer makers.

-Nobade

So, Nobade, I just got a 1968 version of the '94 Winchester in .32 Winchester Special. Am I gonna have problems with the throat when I put my paper patched boolits in this gun? Do you think it'll need any special attention? I've gotten pretty good at wrapping boolits, just not so good at shooting them, yet. I plan on correcting that this summer. mikeym1a

[Nobade]

So, Nobade, I just got a 1968 version of the '94 Winchester in .32 Winchester Special. Am I gonna have problems with the throat when I put my paper patched boolits in this gun? Do you think it'll need any special attention? I've gotten pretty good at wrapping boolits, just not so good at shooting them, yet. I plan on correcting that this summer. mikeym1a

No. PP boolits work quite nicely in the 32 Win Spl. In fact, that is all I ever use in mine.

You know, a funny thing is the standard 30-30 chamber. If you could try to design a chamber that has everything possible wrong with it, that would be the result. No throat, but let's make the neck an extra 1/8 inch longer than the case and let that be the throat. So we have a really long jump to the rifling and a really abrupt start to it. But y'know what? It works! Not optimally but good enough for most work. Beats me, I guess the pressure is low enough to allow it to do what it does. 32 spl. actually has a much more intelligently designed chamber, with a nice start into the rifling usually.

-Nobade

[Nobade]

thanks for that Nobade. that makes a lot of sense. however maybe I got miss understood about what exactly I am referring to.

tha sharp 'angle' I speak of and refer to is the abrupt edge on the groove section of the rifling beginning ... not the throat nor lack thereof.

was just over on the BP Patching section and Lead Pot posted photos of a very nice lead section that includes the throat and lead angle that I refer to. the abrupt rifling beginning on the groove section is the area of concern to me and I do not want to add more throat to any current chamber ... just smooth out the "lead angle" on the rifling.

guess my header was misleading a bit ... should have read {RIFLING LEAD ANGLE} srry for the cornfusion.

Ah, I hear you. Funny thing is, there are lots of chambers out there like you want. Most every 357 mag, 357 max, 44 mag, 45 Colt, and other rifles are chambered like that and most people hate them. They allow too much gas to escape past the boolit before it makes it all the way to the rifling and seals, and are generally difficult to get to shoot accurately. The 458 Win Mag is similar, it has a little step but not much of one and usually starts at .490".

Those type of chambers work beautifully with PP boolits but you normally have to load the ammo to much longer length than is standard so it won't cycle through repeaters. You also end up using boolits much bigger than is normally recommended. But loaded right they usually are extremely accurate and powerful.

I tried something similar a while back. My own 375 Taylor was leaving paper rings in the chamber and I thought if I did exactly what you are describing it would fix it. So I got Dave Manson to make me a neck/throater with no step on the end and a 7 deg/side bevel. I redid the chamber with that (set the barrel back so it wasn't too long) and it did get rid of the paper rings. It also didn't shoot all that accurately any more, and I haven't quite figured out why. I think it has to do with the space around the boolit as it goes from the "open" area between the end of the case and the actual throat. Possibly there is enough space for gas to leak by, I haven't proven anything conclusively but I did get tired of flogging it and it's going to get a different barrel one of these days.

Also what you mention is kind of popular with Orville Loomer of Shiloh fame. He has done a lot with reamers to accomplish exactly what you describe, and it does help PP and black powder quite a bit. Not as good as a tight chamber that won't allow a boolit much over bore diameter, but it does help compared to a factory chamber. You'd have to ask him what happens when you shoot grease groove boolits in a chamber like that. Some say it works, some say they have lost accuracy.

So, lots to think about and play with. Some of it works, some of it not so well.

-Nobade

[bigted]

thanks so much all. so far this is just arm chair theory and hasn't cost a penny yet. just always wonder why of stuff and I cant come to any solid conclusions on all this so far. gonna be a bit more busy with the move for awhile so I gots lotsa time to cogitate and collate.

all me cash has gone POOF ... sunk into property down there so will be a bit for the experimenting as well.